The present invention relates to a progressive scan video production system and magnetic recording/reproducing apparatus which conduct management of the positioning of video material at a half of the frame frequency during transmission or editing of video signals between component apparatuses of the system.
Conventionally, position management and phase lock for video material between the component apparatuses of a video production system of NTSC system have been carried out at 30 Hz. This is because NTSC employs the interlace scan system and its frame frequency is 30 Hz, of which information is integrated in NTSC system. There has been a problem in introducing the progressive scan video system in the NTSC market. The frame frequency of a progressive scan video signal is 60 Hz and not 30 Hz. Therefore, unless an appropriate method is proposed, all the related apparatuses would have to be replaced with progressive scan video signal compatible apparatuses in order to introduce this system. One of such proposed methods is described as a conventional example hereinafter.
FIG. 3 is a block diagram of a configuration of a conventional progressive scan video production system.
The example comprises a recording/reproducing apparatus 1 (hereinafter, VTR) based on the progressive scan TV system, a VTR 20 based on the progressive scan TV system, and an interlace TV sync signal source 5.
In editing a video material, the VTR 1 is used as a reproduction apparatus and the VTR 20 is used as a recording apparatus.
The interlace TV sync signal source 5 outputs interlace reference signals (hereinafter, I_REF), a reference for the management of the frame position and the like of the system. I_REF is a 30 Hz signal synchronizing with an interlace sync signal. Apparatuses other than the interlace TV sync signal source 5, namely the progressive scan VTR 1 and VTR 20, have a I_REF input terminal 1a and a I_REF input terminal 20a provided respectively thereon.
Timing of each apparatus is controlled according to the I_REF, thereby synchronizing the whole system.
A video output terminal 1e of the VTR 1 and a video input terminal 20b of the VTR 20 are connected. During the editing of video material, the video signals recorded on the VTR 1 are input into the VTR 20 via the video output terminal 1e and the video input terminal 20b. The video signals are multiplexed with audio signal and supplementary data such as time code signal. The VTR 20 separates the audio signal and the supplementary data such as time code signal from the multiplexed signal, and re-records a new time code on a tape in the VTR 20 while simultaneously recording the video signals.
In the time code, frame data including time (hour, minute, second) and frame numbers which show the position of the frame are included to be used for positioning the video material during editing or reproduction.
The interlace TV sync signal source 5 supplies I_REF to the I_REF input terminal 1a of the VTR 1 and the I_REF input terminal 20a of the VTR 20. When the video material is edited or reproduced, VTR 1 and VTR 20 are phase locked at 30 Hz according to the I_REF. Besides VTR 1 and VTR 20, needless to say, other peripherals are also controlled at 30 Hz through receiving the frequency of 30 Hz from the I_REF.
Following is a brief description of the progressive scan TV system. (Refer to the broadcasting standard SMPTE292M, SMPTE296M and SMPTE293M for details.)
SMPTE293M (720xc3x97483 Active Line at 59. 94 Hz Progressive Scan Production Digital Representation) is a signal format generally called 525P which is a promising system as a progressive scan TV system with 525 lines. 525P has 525 lines in {fraction (1/60)} seconds among which 483 lines are effective, and one vertical period or {fraction (1/60)} seconds forms one frame.
Therefore, there is no information showing bounds of {fraction (1/30)} seconds in 525P.
SMPTE296M (1280xc3x97720 Scanning, Analog and Digital Representation and Analog Interface) is a signal format generally known as 720P. This is a promising system for a progressive scan TV for high definition TV or HDTV. In 720P, there are 750 lines in {fraction (1/60)} seconds among which 720 lines are effective. One vertical period or {fraction (1/60)} seconds forms one frame. Therefore, there is no information indicating bounds at {fraction (1/30)} seconds in 720P either.
On the other hand, SMPTE292M (Bit-Serial Digital Interface for High Definition Television Systems) is a transmission format called Bit-Serial Digital Interface (hereinafter, SDI) of Y luminance signals and Pb/Pr color-difference signals. SDI can transmit video signals, audio signals and time code signals via single coaxial cable. The progressive scan video signals in the SMPTE296M or SMPTE293M format can be transmitted as digital serial signals by using SDI.
In the progressive scan video production system, there is a common problem in dealing with video signals in both 525P and 720P format. The problem is described below taking 720P as an example.
FIG. 5 and FIG. 6 are abstracts of SMPTE296M. FIGS. 5 and 6 show analog signals and digital signals in the 720P format respectively. They all are progressive scan TV signals.
FIG. 5 shows analog signals in the 720P format. As FIG. 5 shows, the top line of the analog video signal is line 26, the bottom line is line 745, blanking line is from line 746 through line 750 and line 1 through line 25. This format consists of progressive scan video signals with 750 lines in total. There is no information for {fraction (1/30)} seconds or 30 Hz.
FIG. 6 shows digital video signals of 720P. As shown in FIG. 6, in the case of 720P digital signals, the Line Start and the Line End of video signals are controlled by the Start Active Video (SAV) and the End Active Video (EAV). The Top Line and Bottom Line are recognizable through SAV and EAV.
This format consists of progressive scan video signals totaling 750 lines, however, there is no information for {fraction (1/30)} seconds or 30 Hz.
In contrast to progress sequence scan TV signals in the 720P format, the format of the interlace TV signals forms one frame with a frequency of {fraction (1/30)} seconds in two fields, the first and second fields with a frequency of {fraction (1/60)} seconds. Moreover, in the interlace TV signal format, the sync signal format of the first and second fields is different, and there is information for discriminating the first field and the second field.
However, as described above, the progressive sequence scan TV signal format as set forth in FIGS. 5 and 6 does not form fields, therefore there is no information corresponding to {fraction (1/30)} seconds or 30 Hz.
Therefore, in order to introduce the progressive scan video production system into a video production system of which the system is controlled based on information of {fraction (1/30)} seconds, the interlace TV sync signal source 5 which generates information corresponding to 30 Hz (I_REF) had to be included.
FIG.4 shows a block diagram describing the progressive scan VTR 20 as set forth in FIG. 3 in further detail.
Following is the description of FIG. 4.
When video is recorded, recording/reproducing (REC/PB) switches 14 and 17 are connected to the recording (REC) side. The progressive scan video signal input from the video input terminal 20b is recorded on a tape 25 by a rotary head 12 after passing through a recording amplifier 8 and the REC/PB switch 14.
A recorded frame detecting circuit 7 detects the starting point of each frame of progressive scan video signals.
On the other hand, I_REF input from the I_REF input terminal 20a is input into a reproduction frame detecting circuit 11. The reproducing frame detecting circuit 11 generates frame reset signals of 30 Hz and outputs the frame reset signals to the recorded frame detecting circuit 7. The recorded frame detecting circuit 7 resets signals detected from the video input signals which indicate each starting point responding to the frame reset signals, and outputs frame lock signals of 30 Hz to a servo circuit 13. The servo circuit 13 then drives a tape driving motor 26 based on the frame lock signals output from the frame detector 7, and controls running speed of the tape 25. The VTR 20 phase locks the record of the signals.
In this manner, the transmission of the progressive scan video signals from the VTR 1 to VTR 20 can be managed at 30 Hz.
During reproduction, the REC/PB switches 14 and 17 are connected to the PB side. The progressive scan video signals reproduced by the rotary head 12 is output from a video output terminal 20e via the REC/PB switch 14 and a reproduction amplifier 9. The servo circuit 13 drives the tape driving motor 26 according to the frame lock signals output from the reproduction frame detecting circuit 11, and controls running of the tape 25 while the VTR 20 outputs the video signals controlled at 30 Hz.
As it is clearly shown in the above description of the operation, in order to record and reproduce progressive scan video signals in the system controlled at 30 Hz, an apparatus which outputs 30 Hz signals and a cable which transmits such 30 Hz signals are desirable.
The progressive scan video production system and magnetic recording/reproducing apparatus of the present invention comprise a plurality of video apparatuses including at least one recording/reproducing apparatus based on the progressive scan TV system which alternatively transmits progressive scan video signals including at least video signals, audio signals and time code signals, wherein said recording/reproducing apparatus comprises; detecting means for detecting time code signals; signal generating means for generating signals with a half of a frame frequency by detecting a frame position of one of odd and even frame numbers included in the detected time code; and controlling means for controlling phase-sync of frames based on the generated signals with the half of the frame frequency.
With the above configuration, information corresponding to the frequency which is the half of the frame frequency, for example 30 Hz, is generated out of the time code multiplexed to progressive scan video signals. Based on this information, relative relationship between the video signals and location on the tape where the video signals are to be recorded is locked and re-recorded.
Therefore, the progressive scan video production system can be incorporated into the interlace scan video production system without employing an interlace TV sync signal source.
The connection between progressive scan VTRs functioning as a recording apparatus and a reproducing apparatus respectively is simplified, and the out put from the progressive scan VTR functioning as a recording apparatus can be directly routed into the interlace scan video production system.